Nano-porous templates of alumina are commonly used to grow metallic nanowires. The diameters of the nanowires are controlled only by the size of the pore.
There exists four methods for the growth of GaN nanowires. (1) Confined growth of metal nanowires using carbon nanotubes or nanoporous alumina membranes. In the carbon nanotubes the growth of metal is restricted to the diameter of the tubes. In nanoporous alumina it has been suggested that the capillary effect of these anodic pores are responsible for the formation of metal nanowires. (2) Atomic force lithography. (3) Electro deposition. (4) Solid phase arc discharge method.
Currently there exists no method to grow freestanding metallic nanowires.